Charge forming device



March 4, 1947f E. CHANDLER CHARGE FORMINGDEVICE Original Filed Oct. 15,1940 Patented Mar. 4, 1947 UNITED STATES PATENT OFFICE.

by mesne assignments, to Niles- Bement-lond Company, West Hartford,Comb, a'corporation of New Jersey Continuation of application Serial No.361,239, October 15, 1940. This application February 4, 1943, Serial N0.474,736

7 Claims.

This application is a continuation of my application Serial No. 361,239,filed October 15, 1940.

vices, and while not limited thereto, it has particular reference tocarburetors for aircraft engines. I

One of the objects .of the invention is to provide an improved fuel andair proportioning device for an internal combustion engine.

Another object is to provide an improved device applicable to aircraftcarburetors for supplying fuel to the manifold in a manner to compensatefor fluctuations in the weight and other characteristics of air suppliedto the engine under different operating conditions.

In the accompanying drawing:

Fig. 1 is a somewhat diagrammatic sectional view showing an aircraftcarburetor provided with a charge forming device embodying my invention;and

Fig. 2 is a fragmentary sectional view illustrating a modified form ofthe apparatus.

In the drawing, a carburetor body or casing is shown at vI, the samehaving an air intake passage 2 extending therethrough provided at oneend with an enlarged inlet or scoop 3 and at the opposite end having aportion 4 adapted to communicate with an adjacent part (not shown) ofthe manifold structure. Located in the main air passage adjacent the endportion 4 is a fuel supply jet or nozzle 5, and upstream from nozzle 5is a pair of throttle bars or flaps 6 adapted to be turned by means ofshafts I fixed thereto,

said shafts extending completely across the pas sage.

In the passage, somewhat below the scoop portion 3 (Fig. 1), is a.restricted throat or Venturi portion 8. A control device located at therighthand side of the carburetor and generally indicated at 9 isactuated by variation in the pressure differentials between the scoop 3and the throat 8, in a manner to be hereinafter described.

The liquid fuel supplied to the nozzle r jet is derived from a fuel tank10 delivering fuel through a pipe H to a fuel pump l2, whence fuel ispumped through a pipe l3 to a vapor trap and filter device l4, and areturn pipe l5 leads from device l4 back to tank ill in order to returnto the tankvapor rising to the upper part of device M. The fuel passingfrom device l4 passes to a manually adjustable fuel controlllng valveIii-having parallel fixed orifices l1 and I1 and a' parallelspring-loaded power jet Ill. The manual control of the valve 16 isprovided by a. rotary distributing valve l9 upstream from. the orificel1 and movable by an arm 20 fixed thereto, which This invention relatesto charge forming dearm" is shiftable by the pilot through connectionswhich it is not necessary to illustrate. From valve IS the fuel passesthrough a pipe 2| to a main metering orifice or restriction 22, which, 5in this instance, is located in the left-hand wall structure of thecarburetor part of the mamfold. From orifice 22 fue1 passes through apassage 23 toa. pressure control valve 24 which maintains a minimumpressure in the main fuel con- 10 duit, passage 23 being providedintermediate restriction 22 and valve 24 with a rotary controlling valve25. The valve 25 is turned whenever the throttles 6 are moved, and forthis purpose an arm 21, rigid with one of the throttle 15 shafts isconnected by means such as a link 28 to an arm 29 rigidly fixed to valve25. From pressure-controlling valve 24 the fuel passes ghrogigh apassage 30 which leads to the fuel The fuel pump l2, illustrated in Fig.1, is a constant pressure pump including in its structure a casing 3|having a chamber-32in which a rotor 33 is disposed. In the upper part ofthe pump casing a by-pass 34 is arranged leading back from the'dischargeside to the inlet side, and this by-pass is opened and closed by avertically sliding valve 35 which, in the position of Fig. 1, that is tosay, its lowermost position, closes k the-by-pass. The valve 35 isprovided with one or more ports 36 establishing communication betweenthe'pump chamber and a chamber 31 adjacent the under part of a diaphragm38 attached to the valve 35, the up and down movement of the diaphragmbeing effective to raise 35 and lower the valve. Above the diaphragm 38in a chamber}? is a coiled spring 39 acting on the diaphragm, whichspring biases the valve toward a closed position. The spring 39 is acompression spring and the degree of its compression can be adjusted bymeans such as an adjusting screw- 4p having a nicked head accessible atthe exterior of the pump casing.

Fuel. at the under side of the diaphragm 38 can pass to the chamber 38above the diaphragm through a bleed or restriction which, in thisparticular case, includes a small passage 4| below the diaphragm, asmall passage 42 above the diap agm, and an intermediate or connectingpassage 43 of somewhat larger diameter, which last passage, in thisparticular case, is provided with a screen 44.

Fuel passing from the under side of the diaphragm 38 to the upper sidecan pass out-of the casing by way of a. passage 45 to which is connecteda. pipe 45 (of relatively small cross section compared to the main fuelconduit) constituting. a portion of a branch conduit, said pipe 48leading, as hereinafter described, to a. discharge nozzle or vent portwhich, in this particular case, is located in the main air passage 2.

The control device 9 which is affected by changes in the amount of airentering the main air passage is preferably of the diaphragm type andcomprises a, diaphragm 41 clamped between an inner member 48 and anouter member 48 so as to provide a chamber 50 at theleft-hand side ofthe diaphragm and a chamber at the righthand side, Secured to thecentral portion of the diaphragm within the chamber 50 is a valve body52, which valve body, as hereinafter described, is a part of a pilotvalve mechanism which controls the venting of fuel from the branchconduit of which the pipe 46 is a part, and thereby the position ofvalve 35.,

From the Venturi or throat portion 8 of'the main passage, a. controllingair pressure connection is made in a suitable manner to the chamber 50,and in the particular form shown, this includes a passage-53 at thethroat having small suction openings 54. Frompassage 53 a passage 55 isextended to an annular passage 56, and passage 56 communicates with ashort passage 51 leading to chamber 50, and annular passage 56 alsoleads to a restricted passage or bleed 58 having a restricted endportion 59 leading into the chamber 5|.

In the scoop portion 3 are small pressure inlets 60 to a passage 6|extending around-the air passage. This passage 6| communicates with achamber 62 in the right-hand wall structure of the carburetor, and inthe chamber 62. is an aneroid device 63 of usual structure around whichair can circulate, having its interior passage 64 controlled by a valve65 and in communication with a passage 66 leading upwardly and thenlaterally and then downwardly, as shown in Fig. 1, so as to communicatewith the chamber 5| at the right-hand side of the diaphragm 41. Atemperature bulb 61 associated with the aneroid device-63 projects intothe main air passage of the carburetor somewhat .upstream of thethrottle,

bars. 1 I

Reverting to the valve 52 carried by diaphragm 41, it will be seen thatthis valve is adapted to make contact at its left-hand end with, and tobe controlled by, a diaphragm 68 which is marginally clamped betweensuitable members in such a manner that said diaphragm 68 provides ortube 'l'l which projects into the main passage to a slight extent.

As above stated, the valve 24 serves to maintain a minimum pressure inthe-fuel conduitdownstream of the metering restriction 22, In the formshown, it comprises essentially a sliding hollow sleeve I8 having theright-hand'end open and adapted to abut a valve seat I9 in order toprevent fuel from moving into passage 38. v

by a diaphragm 82 biased toward the right by,

a spring 83 and also subject to scoop pressure. The scoop pressure istransmitted to the left-hand side of diaphragm 82 by a passage 84leading from the passage 6|. Thus, the scoop pressure tends to hold thevalve closed, and in order to open it a predetermined pressure of fuelhas to be built up in that portion of the fuel conduit upstream of thevalve. I

In the operation of the device, .fuel is supplied by pump l2 to the mainfuel conduit and the main metering restriction 22 in said conduit. Acertain amount of the fuel on the delivery side of the pump passesthrough the valve 35 into the chamber beneath diaphragm 38 v and bleedsaround this diaphragm into the upper chamber 38, and thence to thebranch conduit. If valve 52 is in the open position, fuel passes-throughthe branch-conduit or auxiliary hydraulic connection '46, 14, 18, ll,16, 11, into the manifold. Spring 39 normally holds the valve 85 intheclosed position, but upon excess pressure being developed at thedischarge side of the pump, the

a valve can rise under some conditions in order to permit fuel to passback to the inlet side of the pump. 1

. Assuming that the engine is in operation at a relatively high speed,in which case there willbea considerable pressure'diflerentialbetweenthe scoop and throat portions of the air passage, and

\ the throttles are moved toward the closed position so as to reduce thespeed, the pressure differential between scoop and throat will bereduced,

' and assuming that when the engine is at high a portion of theleft-hand wall of chamber 50'.

A biasing spring 69, which may be a coil spring and which is located inchamber 5|, acts on diaphragm 41 so as normally to hold valve 52 againstdiaphragm 68 and diaphragm 68 in turn against a valve seat 10controlling a passage 1| which is adapted to vent the branch fuel pipe46 in a suitable manner, Spring 69 is a compression spring, and thedegree of its compression can be controlled by suitable meanssuch as anexteriorly accessible adjusting screw 12 connected to a cup 13 receivingthe right-hand end of the spring.

The valve seat 10 is at-the exit of a small chamber 14 at the left-handside of the secondary diaphragm 68, The pipe 46 is in communication witha passage 15 in the carburetor wall, which passage leads to the smallchamber 14, and if fuel can pass through chamber 14 and valve seat 10,it will flow into a passage 16. In the particular form shown, thepassage 16 is arranged to conduct any vented fuel to the main passage ofthe carburetor upstream of the, throttles, and for this purpose passage16 leads to a small nozzle speed the valve 52 is closed, the change ofspeed will be effective to open the valve. With the valve 52 closed,thereby closing the branch conduit intermediate of its ends, acertainamount of hydraulic pressure will have been built up in theconduit and in the chamberv above the diaphragm 38, assisting the actionof the spring 39, which biases the valve 35 toward the closed position,and the valve 35 will be closed. The opening of the valve 52 will beeffective to enable fuel to pass freely out of the branch conduit, whichwill reduce the pressure above the diaphragm 38 and enable the pressurebelow said diaphragm to raise the diaphragm and valve 35, moving thevalve toward the open position so that fuel is bypassed back to theinlet side of the pump, with the result that the delivery of fuel fromthe pump decreased. In the operation of venting surplus fuel from thebranch connection, this relatively small quantity of fuel may be carriedinto the manifold, as above described, although this is merely byway ofexample, and other arrangements can be provided in that respect.Assuming now that the speed of the engine is again increased, theresulting increase of air pressure differential in the air passage willcause the valve 52 to be closed again, thereby closing the branchconduit intermediate of its ends and causing pressure to be built upagain in that portion which is on the fuel-receiving side of the valveseat I0. As pressure builds up in the branch conduit, it causes pressureto be built up above the diaphragm of the device controlling theeffective output of the pump, thereby causing the by-pass valve 35 to beclosed, and thus supplying more fuel to the main conduit, as isdesirable under these conditions. With a regulating device of the typeabove described, the result "of the building up of pressure in thechamber above the diaphragm is to close down the by-pass valve of thepump so that the pump cannot act in the normal manner but on the otherhand, by the elimination of the by-pass action, provides increaseddischarge pressure and an increased sup- .plyof fuel to the fixedmetering orifice.

It is also to be understood that, with the throttle in any given settingduring engine operation, the valve 52 will have movement from time totime as conditions of air pressure, air density, temperature, etc.,vary, so as to cause corresponding compensating movements of theregulating valve which is effective in regulating the amount of fuelsupplied by the pump to the main metering orifice.

It isimportant to note that the spring 39 of the regulating device hasthe function of acting upon and controlling the position of theregulating valve throughout the entire range of engine operation, saidspring throughout said range biasin'g said valve to a closed position inthis particular case. The pressure of thefuel under the diaphragm 31acts upwardly, opposing the action of this spring throughout the rangeof engine operation. The pressure of the fuel above the beneath thediaphragm, act downwardly assisting this spring throughout the range ofengine operation. The fuel at the upper part of the diaphragm can passout of the casing of the regulating device to a discharge, which isprovided in this particular case by the pipe 46 and its associatedconnections, and'by building up the pressure of the discharge throughthe closing of the discharge or vent connection, the position of theregulating valve can be changed in accordance with the varying airsupply to the engine. The regulating valve is, of course, moved in theclosing direction at any point in the range of engine operation when,the branch connection being closed by the air-supply-controlled valve52, the pressure above the diaphragm is increased to a point where it,conjointly with the action of the spring 39, will overcome the pressureon the under side of the diaphragm.

In the modified form of the apparatus shown in Fig. 2, the system is thesame as above described, but the regulating device for controlling thesupply of fuel from the pump to the fixed metering orifice is of adifferent kind. Here the pump casing is indicated at 85, the same havingan inlet 88 from a fuel tank connection ll. Within the pump casing is animpeller 81 having in association therewith an enclosing pivoted liner88 provided at the inlet side of the pump with an inlet port 89. Thispump, as illustrated, V

is of the variable capacity construction described and claimed in UnitedStates Patent No. 2,318,-

337, issued to Arthur G. Schlosser, on May 4, 1943. The liner 88 ispivoted in the casing at 90, and the construction is such that, as theliner is swung upwardly from the position shown in Fig. 2, the amount offuel being discharged by the pump is decreased, whereas when the lineris swun downwardly again the amount of pump discharge will be increased,this being due to the change in capacity of the passage carrying liquidfrom the inlet to the outlet. Within the liner at the discharge sidethereof are passages SH, 92 leading around to and in free communicationwith a narrow chamber 93 arranged in the pump casing at the dischargeside, and the chamber 93 is in free communication with a chamber 94arranged at an angle to the horizontal in the upper part of the pumpcasing structure. The chamber 94 is located beneath a diaphragm 95connected to a rod 95 pivoted at its lower end 91 to the liner 88 so asto be capable of swinging the liner up and down. Above the diaphragm 95is a chamber 98,. Withinthe chamber 98 is a coil spring 99 adjustable bya screw Hill, said spring acting against the diaphragm in such'a manneras to bias the rod 96 in a direction to hold the liner in its lowermostposition. From the chamber 94 a bleed IDI lead upwardly to providecommunication with the space above the diaphragm, said bleed Hllcommunicating with a passage I02 leading into the upper chamber at oneside of the latter. The passage I02. is not only in communication withthe space beneath the diaphragm, but also in this instance connectsdirectly with'a pipe 46' which corresponds to pipe 46 previouslydescribed, and is opened and closed by an air-supply-controlled valve inthe manner previously described.

In operation this form of regulating device for regulating the amount offuel discharged by the pump acts in substantially the same manner as theregulating device of Fig. 1.

By my improvements a very effective and positive-control of theproportioningof fuel and air is provided, the control being quitesensitive and at the same time reliable in operation. A

very definite advantage arises from the fact that the pressure resultingfrom differences of air pressure' in the scoop and throat, respectively,is not employed by connecting it directlyby ,me-

chanical means to a heavy device or member re- 4 quiring shifting foraffording control of the metering of the fuel. In the improvedapparatus, on the other hand, the relatively small pressure resultingfrom the differences of pressure in the scoop and throat, respectively,is used only indirectly for effecting the metering of the fuel, and inthis operation, as appears from the above description, the fuelpressure, which is al ways considerably greater than the air pressuredeveloped by the air pressure differentials, is made use of to build upin the branch connection from the main fuel conduit a hydrauliccontrolling pressure which is substantial in amount and can be used forcontrolling purposes effectively and with comparative ease.- As the fuelmetering mechanism is, to a large extent, controlled by the relativelylarge forces of fuel pressure as distinguished from air intake pressuredifferential, the tendency toward inaccuracy of fuel metering is verymaterially reduced. This large metering force also makes it possible touse very small valves for actuating the regulating device in place ofrelatively large diaphragms that have to be used when the metering forceis small.

A further definite advantage arises from the 7 a relative simplicity ofthe apparatus and from.

the ready accessibility of the different partsfor adjustments andrepairs-if and when these are necessary. A simple fuel-regulating valvestructure is employed, the valve being shifted directly by increases anddecreases of pressure in a hydraulic controlling passage which is abranch of building up of pressure in the branch hydraulic connection,and the pressure in said connection acting directly on thefuel-regulating device. If repairs to the fuel-regulating valvestructure on the one hand or to the air-supply-controlled valve deviceon the other hand are necessary, each can be manipulated independentlyof the other, and of course it is possible to place these devices atvarious locations relatively to each other and to the carburetor body,so that the apparatus can be assembled and installed to a large degreein accordance with the dictates of convenience, saving of space, etc. Insome cases the fuel can be supplied to the engine in other:

locations than within the carburetor structure. While two embodiments ofthe invention are shown and described, it will be apparent' that theinvention is susceptible of numerous other embodiments, and that variouschanges in the organization of parts and in the details can be madewithout departing from the principles of 1 the invention or .the scopeof the claims. I

What I claim is: v U 1. In a carburetor, means providing an air in- .letpassage,-means therein producing a differential of air pressures varyingas a function of air flow, a fuel pump, regulating means to vary theeffective. output of said pump, 'a main fuel I conduit extending fromthe pump to a discharge nozzle in the air passage, a pressure'controlvalvev in the conduit to maintain a minimum pressure in said conduit, ametering restriction in said conduit, mechanism for varying the fuelpressure on said restriction comprising a restricted fuel by-passconduit extending from said main conduit to anauxiliary discharge portin the air passage, means subjected to' the differential air 1 pressuresto control the fuel flow from said bypass conduit and to therebymaintain back pressure proportional to said difierential of airpressures, and'fluid pressure responsive means subjected respectively tothe pressures in said main conduit and said by-pass' conduit connectedto operate said pump regulating means whereby to maintain the fuel flowthrough said main conduit proportionalto the measured air flow.

2. A carburetor for an internal combustion engine, comprising incombination, a first conduit for conveying air for combustion purposesto said engine, means in said first conduit for producing therein adifferential of air pressures which varies over a predetermined range asa function of the quantity of air flowing thru said conduit, means forsupplying fuel under superatmospheric pressure, a second conduit forconveying fuel from said fuel supply means to said engine, a meteringrestriction in said second conduit effective to control the flow of fueltherethru as a function of the fuel pressure diiferential thereacross,said restriction being so proportioned that said fuel pressuredifferential must vary over a range greater than the range of said airpressure differential in order to maintain fuel flow proportional to airflow, first valve means for controlling the fuel flow thru said secondconduit, a third conduit supplied with fluid fuel from said source andincluding -a restriction, an

expansible chamber forming a part of said third conduit and having amovable wall subject on its opposite side to the pressure in, saidsecond conduit, said wall being operatively connected to said firstvalve means for positioning the same, pressure multiplying means for,controlling the pressure in said chamber, said pressure multiplyingmeans including second valve means for controlling the discharge offluid from said third in said differential of air pressures and a valveoperated by said diaphragm, a fuel-carrying branch conduit having meanscooperating with said valve whereby said branch conduit is opened andclosed, a fuel pump, regulating means to vary the effective output ofsaid fuel pump comprising an expansible chamber connected to said branchconduit and having a-unitary wall structure movable in a direction toexpand said chamber under the influence of the back pressure of fueltherein created by the closing'of said branch conduit, a spring actingon said unitary wall structure and constantly biasing it in a directionto assist such back pressure, the other side of said unitary wallstructure being subject to the pressure of the fuel being discharged bythe pump, a main fuel conduit extending from the pump to a dischargenozzle in the air passage, a metering restriction in themain conduit,and a pressure control valve in the main conduit intermediate themetering restriction and said discharge nozzle.

4. In a fuel and air proportioning device for an internal combustionengine, means providing an air intake passage, means in association withsaid passage for setting up a difierential of air pressures varying as afunction of air flow, a control device connected to said last-namedmeans comprising a first diaphragm movable by variation of saiddifferential of air pressures and a valve operable by said diaphragm, afuel-carrying branch conduit arranged to be opened and closed by saidvalve as the air pressures vary, a

regulatin device for the fuel supply including a pair of expansiblechambers separated by a'movable unitary wall structure, one of saidchambers being connected to said branch conduit so' that on the closingof said branch conduit by said valve back pressure of fuel is built upon one side of said wall structure, a fuel pump, a main conduit leadingfrom said pump to a discharge nozzle in the air passage, means forsubjecting the chamber on the other side of said wall struc- I sureswhose difference varies over a predetermined range as a function of thequantity of air flowing thru said conduit, means for supplying fuelunder superatmospheric pressure, a second conduit for conveying fuelfrom said fuel supply means to said engine, a. fixed meteringrestriction in said second conduiteifective to control the flow of fueltherethru as a function of the fuel pressure differential thereacross,said restriction being so proportioned with respect to said airdifferential pressure producing means that said fuel pressuredifferential must vary over a range greater than the range of said airpressure differential in order to maintain fuel "fiow proportional toair fiow, a passage connected in parallel with said restriction, a valvein said passage opening in the direction of fuel flow therethru, meansbiasing said valve toward its closed posi-; tion, said valve beingoperable to open position against the action of said biasing means inresponse to an increase in said fuel pressure differential above apredetermined value by virtue of the pressure differential actingdirectly on the valve itself, and means responsive to said air pressuredifferential for controlling said fuel pressure differential andeflective in response to each increment of air pressure differential toproduce a greater increment of fuel pressure differential, saidlast-named means including a valve for controlling the pressure on oneside of said restriction, three expansible chambers, first flexiblediaphragm means separating two of said chambers, means for supplyingsaid two chambers with air at said two unequal pressures, means forsupplying the third of said chambers with fuel at a pressure indicativeof the pressure on said one side of said restriction, second diaphragmmeans of smaller area than said first diaphragm means and to permit asmall increment of said air pressure differential to balance a largerincrement of said fuel pressure, and means operatively connecting bothsaid diaphragm means to said valve so that an increase in the differenceof said two air pressures causes a fuel fiow increasing movement of saidvalve and a variation in the fuel pressure in said third chamber in asense indicative of an increased .fiow thru said restriction causes afuel flow decreasing movement of said valve..

6. A carburetor for an internal combustion engine, comprising a firstconduit for conveying air for combustion purposes to said engine, meansassociated with said first conduit for producing two unequal airpressures whose difference varies over a predetermined range as afunction of the quantity ofair flowing thru said conduit. an auxiliarycontrol device to be operated in accordance with the. load on saidengine, means for supplying fuel under superatmospheric pressure, asecond conduit for conveying fuel from said fuel supply means to saidengine, a fixed metering restriction in said second conduit effective tocontrol the flow of fuel therethru as a function of the fuel pressuredifferential thereacross, said restriction being so proportioned withrespect to said air differential pressure producing means that said fuelpressure differential must vary over a range greater than the range ofsaid air pressure differential in order to maintain fuel pressuredifferential and effective in response to each increment of air pressuredifferential to produce a greater increment 'of fuel pressuredifierential, said last-named means including a main valve in said fuelconduit for regulating the pressure on one side of said' restriction, adiaphragm for operating said main valve, an expansible chamber on theopposite side of said diaphragm from said main valve, a first restrictedpassage connecting said chamber to said second conduit at a pointthereinwhere the pressure is regulated by said main valve, a second restrictedpassage controlling the flow of fuel from said chamber, pilot valvemeans for controlling one of said restricted passages, and meansresponsive to the difference of said air pressures for operating saidpilot valve means, said pilot valve means and said chamber beingeffective in response to a small increment of said air pressuredifferential to operate said main valve to produce a larger increment ofsaid regulated fuel pressure.

,7. A fuel and air proportioning device for an internal combustionengine, comprising in combination, a first conduit for conveying air forcombustion purposes to said engine, means associated with said firstconduit for producing two unequal pressures whose difference is ameasure of the rate of fiow of air thru said conduit, means forsupplying fuel under superatmospheric pressure, a second conduit forconveying fuel from said fuel supply means to said engine, a meteringrestriction in said second conduit effective to control the flow of fueltherethru as a function of the fuel pressure differential thereacross. amain valve for regulating the pressure in said second conduit on oneside of said restriction, an

expansible chamber having a movable wall subject to the pressure in saidchamber acting thereon in one direction and to the regulated fuelpressure in said second conduit on said one side of said restrictionacting thereon in the opposite direction, said wall'being operativelyconnected to said main valve for positioning the same, a restrictedinlet passage connecting said chamber to said second conduit at a pointtherein where the pressure is regulated by said main valve, a restrictedoutlet passage connecting the interior of said chamber to a pointmaintained at a lower pressure, pilot valve means for controlling one ofsaid restricted passa es, and means responsive to the difference of saidair pressures for operating said pilot valve means.

MILTON E. CHANDLER.

REFERENCES CITED The following references are of record in the file ofthispatent:

UNITED STATES PATENTS Number Name Date 1,909,469 Hubbard May 16, 19332,002,483 Kimball May 21, 1935 2,165,447 Browne July 11, 1939 2,224,472Chandler Dec. 10, 1940 2,264,347 Udale Dec. 2, 1941 2,281,411 CampbellApr. 28, 1942 2,316,300 Udale Apr. 13, 1943 2,339,650 weiche "Sept. 28,1943 FOREIGN PATENTS Number Country Date 367,310, Italian Apr. 15, 1938523.895 British July 25, 1940 846,774 French Sept. 28, 1939

